              (certificate-request? ext-container)
              (instance? List ext-container))
          (string? oid)]
-   :post [(map? %)]}
+   :post [(extension? %)]}
   (-> (ExtensionsUtils/getExtension (javaize ext-container) oid)
       clojureize))
 

  "Given an object which contains a private key, extract and return it."
  [key-object]
  {:pre [(keypair? key-object)]
   :post [(instance? PrivateKey %)]}
  (CertificateAuthority/getPrivateKey key-object))
  (instance? X509CRL x))

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;;; Internal

(defn clojureize
  "Convert a Java data structure returned from a Java utility method into a
